In the deployment of underwater sound sources and instrumentation, the object being deployed may consist of a cylindrical housing or member containing transducers, electronic gear, etc., to which is attached a second cylindrical housing or member of essentially the same diameter which may contain weights, batteries or flotation means including ropes or cables. Reliable automatic separation is necessary after deployment. The usual means for fastening such cylindrical sections together involves forming or attaching of a ring or ridge at the adjoining ends with a full circle type clamp which bridges across these rims or ridges and which may be tightened by a turnbuckle or similar fastening means. One such device which has been used extensively is the Vee Band clamp maufactured by Aeroquip Corporation. While such devices are entirely satisfactory in most instances, applicant has been confronted with an application wherein the diameter of the assembly closely approaches that of the airborne torpedo envelope in which the assembly is carried, severely limiting the space for such fastening means. In addition, certain longitudinal fin members bridge across the joint between the two cylindrical housings. There are three such fin members which are fastened to the lower cylinder and which (prior to release) are held in a restricted position tightly against the side of the upper housing member. With these fin members installed as described, a release band in the form of a continuous rigid structural circle of significant thickness becomes impractical. The deployment system for the particular sonar device for which the present invention was devised requires that this separation mechanism not significantly add to the overall diameter of the cylindrical housing snce the sonar is to be launched from a standard airborne torpedo envelope. In addition, the available standard types of coupling assemblies for this general application are smewhat expensive, and since the application for which the present separation device has been devised is for an expendable unit, minimum costs are highly desirable.